The prior art suggests that polyhydrazides are degraded in sulfuric acid. Optically anisotropic solutions of (co)polyhydrazides in concentrated (at least 99.5%) sulfuric acid are not taught in the art.
In the solutions of this invention, there is some degradation of the polymeric species (e.g., as evidenced by a fiber exhibiting a lower inherent viscosity value than the polymer from which the spinning solution was prepared), but the solutions are sufficiently stable to permit preparation of shaped articles which exhibit desirable properties, e.g., high strength fibers.